A good vendor will often provide insights and a documented professional opinion, which can serve as third-party confirmation.

Second position lienholder have done some shady stuff in order to delay a loss, including filing suit against all parties or trying to obtain a temporary restraining order.

But unrelated parties who may move out w/o the others it does get to be a bit more tricky. 

Expect to allocate less time  towards management functions if self-performed or more favorable management fee structures if 3rd party management companies are utilized (which ties back to #1, as well).

However, you would have to rework your current contract to be subject to SS approval  (which the buyer may or may not be into),or sell to another party, and if you are getting financing for the new house, that will likely fall apart as well. 

If there is no Operating or partnership agreement tell both parties to never invest in this way again.

We use a 3rd party company that specializes in only property management trust accounting (nothing else), and they reconcile the bank account every single day.

You want to make both parties happy.Most wholesalers fail because they are chasing the spread (their money) and not focused on helping the seller and providing a win-win for the buyer.

Is it worth having tenants use a 3rd party service/app for collecting rent, doing maintenance requests, etc?

In this case, we saved the transaction by understanding what mattered most to each party and finding a way forward.What’s the most unique concession a seller has ever asked for in a deal?